Modem (modulator/demodulator) communications is a well known method of asynchronous serial data communications between two computers or other types of electronic equipment. In a typical environment, a modern modem is connected to a local personal computer (PC) through a serial communications link. The modem is then connected through a public telephone network to a remote location in which a corresponding modem is also connected. The corresponding modem is also connected to a remote computer such as a personal computer through a serial communications link. This allows direct communication between the local personal computer and the remote personal computer over the telephone network. The two modems handle the conversion of digital data into voice band signals for transmission through the telephone network in a full duplex fashion following a variety of CCITT telecommunications standards.
A local area network (LAN) connects a number of personal computers and peripherals together for sharing information and resources. LANs can be connected in a variety of topologies (star, bus, token ring, etc.), operate at different speeds and protocol levels (Ethernet, Arcnet, etc.) use a variety of packet protocols IPX (Internetwork Packet Exchange), TCP/IP (Transmission Control Protocol/Internet Protocol), etc.), all under the control of a variety of network operating systems (Novell Netware, UNIX, etc.).
Typically a PC connected to a LAN communicates with off-LAN computers through a dedicated modem attached only to that PC. The dedicated modem communication does not go through the LAN but rather from the PC through the modem, over a telephone network to the remote computer. Software has been made available which allows a second PC on the network to communicate through the LAN to the modem attached to the first PC for communication to an off-LAN computer having its own dedicated modem. That software allows the second PC to use the modem attached to the first PC to communicate to the off-LAN or remote computer by transferring control and data information over the LAN to the modem attached to the first PC to accomplish the remote communication. This is a cumbersome and expensive method of sharing modem communication through a LAN because the first PC having the modem attached is effectively unavailable for users while modem communication with a non-modem-PC is in effect.
There is therefore a need in the art for special purpose intelligent LAN modem nodes which allow PCs on a LAN to share modem resources for off-LAN communications and which also allows off-LAN PCs access to network resources without tying up any PCs on the network.